Bole epiphytic lichens as potential indicators of environmental change in subtropical forest ecosystems in southwest China

Lichen epiphytes are applied as excellent environmental indicators worldwide. However, very little is known about epiphytic lichen communities and their response to forest dynamics in subtropical China. This paper proposes the applications of the cover, diversity, and functional traits of epiphytic lichens to assess environmental changes associated with succession in subtropical forests of southwest China. Bole lichens were sampled from 120 plots of eight representative forest types in the Ailao Mountains. Total cover, species richness, diversity and community structure of bole lichens differed significantly among forest types, and the highest cover and diversity occurred in the Populus bonatii secondary forest (PBSF). Sixty-one indicator species were associated with particular forest types and more than 50% occurred in the PBSF. Both cover and diversity of most lichen functional groups varied regularly during forest succession. Lichen pioneer species were not displaced by competitively superior species as succession proceeds and cyanolichens were more prevalent in secondary forests. The results also highlight the importance of habitat variables such as canopy openness, host diversity, forest age, tree size, the size of the largest tree, tree density, and basal area on the lichen community. Consequently, our findings support the notion that epiphytic lichens, in terms of cover, diversity, species composition and functional traits can be used as effective indicators for large-scale and long-term forest monitoring. More importantly, the narrowly lobed foliose group was the best candidate indicator of environmental conditions in this region. The combined application of lichen indicator species and functional groups seemed to be a more reliable and more powerful method for monitoring forest dynamics in subtropical montane ecosystems.     

Epiphytic lichens and bryophytes of forest ecosystems in Tuscany (Central Italy)

The distribution of epiphytic bryophytes and lichens on three species of trees (Quercus ilex, Quercus cerris and Fagus sylvatica, representing the forest ecosystems of central Italy at low, medium and high elevations, respectively) was examined with respect to host specificity and habitat differences. Although most species were host-specific, the results suggested that habitat characteristics are more important than phorophyte properties in determining the distribution of lichens and bryophytes. Factors affecting the diversity of the epiphytic flora were different for lichens and bryophytes. In the case of lichens, climatic parameters and forest monospecificity were important factors, whereas tree cover (i.e. shade) and to a certain extent the number of available trees seemed more important for bryophytes.     

Tree age‐dependent changes among epiphytic bryophyte communities in Mediterranean environments. A case study from Sicily (Italy)

Abstract

The epiphytic bryophytes inhabiting trees of different size/age in a Quercus ilex wood from Madonie Mountains (northern Sicily, Italy) were studied with the purpose of describing the changes that take place in the bryophyte stratum during the tree lifespan. Results indicate an increase of bryophyte cover combined with a progressive decrease of epiphytic lichens and the existence of an active process of species and community substitution. The way these processes take place corresponds to a succession sequence, which is characterised by a high number of pioneer species on the youngest trees and a sharp decline of species number on middle‐aged and old trees due to the great spread of Leptodon smithii and a few other pleurocarpous mosses. The comparison of these traits to those from central Spain evidences differences in patterns of tree colonisation by epiphyte bryophytes between the two areas and suggests that climatic conditions play a chief role in the epiphytic bryophyte establishment and succession in Mediterranean areas.     

Removal of secondary compounds increases invertebrate abundance in lichens

We investigated how lichen carbon-based secondary compounds (CBSCs) affect abundance of invertebrates in five lichen species growing on the forest floor (Cladonia rangiferina, Cladonia stellaris) or on tree trunks (Evernia prunastri, Hypogymnia physodes, Pseudevernia furfuracea). To do this, CBSCs were removed by rinsing lichen thalli in acetone (which has no adverse effects on the lichens) and the lichens were re-transplanted in their natural habitat. After 4 months there was higher abundance of mites, springtails and spiders in the three epiphytic lichens that had their CBSC concentrations reduced. The increase in predatory spiders following CBSC reduction suggests that the compounds have multitrophic consequences. The acetone treatment reduced the number of nematodes in four of the lichen species. Given that lichens serve as important habitats for a diverse range of invertebrates, increased knowledge of how lichen CBSCs may regulate their abundance helps us to better understand the role that lichens and their defence compounds play in structuring forest food webs.     

Dynamics of interaction between lichens and fallen deadwood in forest ecosystems of the eastern Baikal region

Successional stages of epixylic lichens in conjunction with fallen deadwood decomposition were studied in the eastern Baikal region. It was found that lichens passed through four stages of epixylic succession: from the epiphytic and epixylic stages to the epigeic stage. It was also determined that lichens could inhibit the decomposition of the higher layer of fallen deadwood, which served as a substrate to them.     

云南哀牢山原生林及次生林群落附生地衣物种多样性与分布

附生地衣是森林附生植物的重要类群之一, 在维护森林生态系统的物种多样性以及水分和养分循环等方面发挥着重要作用。作者于2005年12月至2006年5月利用树干取样法调查了云南哀牢山徐家坝地区原生山地常绿阔叶林及其次生群落栎类萌生林、滇山杨(Populus bonatii)林和花椒(Zanthoxylum bungeanum)人工林中525株不同种类和径级树木距地面 0–2.0 m处附生地衣的组成和分布, 并收集了各个群落地面上凋落的地衣, 分析了林冠层附生地衣的物种组成。研究结果表明, 该区森林中附生地衣物种比较丰富。共收集到附生地衣61种, 分属17科29属, 其中原生林、栎类萌生林、滇山杨林和花椒人工林分别有51、53、46和23种。在树干距地面 0–2.0 m位置, 各群落中的附生地衣组成明显不同;但在林冠层中, 各群落内的附生地衣基本相似。原生林中附生地衣种类较多, 但分布不均匀。树干附生地衣的Shannon-Wiener和Simpson多样性指数以栎类萌生林最高, 分别为2.71和0.89;花椒林和滇山杨林次之, 分别为2.43–2.45和0.88–0.89;原生林最低, 为1.25和0.67。树干方位、宿主种类和宿主径级等都对附生地衣的物种组成和多样性有着重要影响, 附生地衣更多地出现于树干南向方位, 云南越桔(Vaccinium duclouxii)的附生地衣最为丰富, 胸径5.0–25.0 cm的树木上附生地衣较多。哀牢山山地森林群落中丰富的附生地衣种类及物种多样性在维系本区山地森林生态系统生物多样性格局方面具有重要的作用。     

Topographic and forest-stand variables determining epiphytic lichen diversity in the primeval beech forest in the Ukrainian Carpathians

The Uholka-Shyrokyi Luh area of the Carpathian Biosphere Reserve is considered the largest and the most valuable primeval beech forest in Europe for biodiversity conservation. To study the impact of different topographic and forest-stand variables on epiphytic lichen diversity a total of 294 systematically distributed sampling plots were surveyed and 198 epiphytic lichen species recorded in this forest landscape, which has an uneven-aged structure. The obtained data were analysed using a non-metric multidimensional ordination and a generalized linear model. The epiphytic lichen species density at the plot level was mainly influenced by altitude and forest-stand variables. These variables are related to both the light availability i.e. canopy closure, and the habitat diversity, i.e. the developmental stage of the forest stands and the mean stem diameter. We found that lichen species density on plots with a relatively open canopy was significantly higher than on plots with a fairly loose or closed canopy structure. The late developmental stage of forest stands, which is characterized by a large number of old trees with rough and creviced bark, had a strong positive effect on lichen species density. In the Uholka-Shyrokyi Luh primeval forest the mean stem diameter of beech trees significantly correlated with lichen species density per plot. Similar trends in the species diversity of nationally red-listed lichens were revealed. Epiphytic lichens with a high conservation value nationally and internationally were found to be rather abundant in the Uholka-Shyrokyi Luh area, which shows its international importance for the conservation of forest-bound lichens.     

Tree hollows can affect epiphyte species composition

Tree hollows often harbor animals and microorganisms, thereby storing nutritive resources derived from their biological activities. The outflows from tree hollows can create unique microenvironments, which may affect communities of epiphytic organisms on trunk surfaces below the hollows. In this study, we tested whether the species richness and composition of epiphytic bryophytes (liverworts and mosses) and lichens differ above and below tree hollows of Aria japonica and Cercidiphyllum japonicum in a Japanese temperate forest. The species richness of epiphytic bryophytes and lichens did not differ above and below hollows; however, the species composition of bryophytes differed significantly above and below hollows. Indicator species analyses showed that the moss species Anomodon tristis and the liverwort species Porella vernicosa were significantly more common below than above hollows, while the liverwort species Radula japonica and four lichen species, including Leptogium cyanescens, occurred more frequently above than below hollows. Our results highlight that tree hollows can produce unique microenvironments on trunk surfaces that potentially contribute to the maintenance of epiphytic diversity on a local scale.     

The effect of the substrate on the growth and reproduction of the lichens Cladonia rangiferina and C. mitis

The growth rate and percentage of fertile individuals were studied in the lichens Cladonia rangiferina and C. mitis growing on various substrates in a heath-lichen pine forest and a bilberry-cowberry pine forest with Pleurozium and other mosses, both on the White Sea coast. The substrates were soil, rocks, and pine wood. The proportion of different forms of C. rangiferina growing on the same substrate was compared between the two forest types. C. rangiferina f. rangiferina was more abundant on soil, while C. rangiferina f. crispata dominated on wood. The effect of the substrate on the development of different lichen forms is discussed. The maximum growth rate and the maximum percentage of fertile individuals were recorded in the lichens growing on soil; these parameters were minimal in the lichens growing on wood. These differences were more pronounced in C. rangiferina than in C. mitis. The effects of the nutritive quality and the humidity of the substrate on the growth rate and apothecia formation in lichens are discussed.     

Hidden crown jewels: the role of tree crowns for bryophyte and lichen species richness in sycamore maple wooded pastures

Tree crowns typically cover the vast majority of the surface area of trees, but they are rarely considered in diversity surveys of epiphytic bryophytes and lichens, especially in temperate Europe. Usually only stems are sampled. We assessed the number of bryophyte and lichen species on stems and in crowns of 80 solitary sycamore maple trees (Acer pseudoplatanus) at six sites in wooded pastures in the northern Alps. The total number of species detected per tree ranged from 13 to 60 for bryophytes, from 25 to 67 for lichens, and from 42 to 104 for bryophytes and lichens considered together. At the tree level, 29 % of bryophyte and 61 % of lichen species were recorded only in the crown. Considering all sampled trees together, only 4 % of bryophyte, compared to 34 % of lichen species, were never recorded on the stem. Five out of 10 red-listed bryophyte species and 29 out of 39 red-listed lichen species were more frequent in crowns. The species richness detected per tree was unexpectedly high, whereas the proportion of exclusive crown species was similar to studies from forest trees. For bryophytes, in contrast to lichens, sampling several stems can give a good estimation of the species present at a site. However, frequency estimates may be highly biased for lichens and bryophytes if crowns are not considered. Our study demonstrates that tree crowns need to be considered in research on these taxa, especially in biodiversity surveys and in conservation tasks involving lichens and to a lesser degree also bryophytes.     

Nitrogen deposition drives lichen community changes through differential species responses

Nitrogen (N) deposition has increased globally over the last 150 years and further increases are predicted. Epiphytic lichens decline in abundance and diversity in areas with high N loads, and the abundance of lichens decreases along gradients of increased deposition. Thus, although N is an essential nutrient for lichens, excessive loads may be detrimental for them. However, these gradients include many correlated pollutants and the mechanisms behind the decline are thus poorly known. The aim of this study was to assess effects of N deposition, alone, on the epiphytic lichen community composition in a naturally N‐poor boreal forest. For this purpose, whole spruce trees were fertilized daily with N at five levels, equivalent to 0.6, 6, 12.5, 25, and 50 kg N ha^?1 yr^?1, during four consecutive growing seasons (2006–2009), and changes in the abundance of lichens were monitored each autumn from the preceding year (2005). The studied lichen communities were highly dynamic and responded strongly to the environmental perturbation. N deposition detectably altered the direction of succession and reduced the species richness of the epiphytic lichen communities, even at the lowest fertilization application (6 kg N ha^?1 yr^?1). The simulated N deposition caused significant changes in the abundance of Alectoria sarmentosa, Bryoria spp., and Hypogymnia physodes, which all increased at low N loads and decreased at high loads, but with species‐specific optima. The rapid decline of A. sarmentosa may have been caused by the added nitrogen reducing the stability of the lichen thalli, possibly due to increases in the photobiont: mycobiont ratio or parasitic fungal attacks. We conclude that increases in nitrogen availability, per se, could be responsible for the reductions in lichen abundance and diversity observed along deposition gradients, and those community responses may be due to physiological responses of the individual species rather than changes in competitive interactions.     

Evaluating the conservation status of epiphytic lichens of Italy: A red list

Despite the fact that Italy is among the lichenologically best known areas worldwide, a national red list of lichens is still lacking. The aim of this work was to provide a red list of the epiphytic lichens of Italy which could facilitate the inclusion of lichens in national conservation plans. The evaluation of the species against International Union for Conservation of Nature (IUCN) criteria was based on data from multiple sources which represent the best available information on the epiphytic lichens of Italy. The species were assigned to the IUCN categories mainly using criteria D and B. A total of 368 species were evaluated: for 23 species, information is missing from more than 50 years and they were listed as regionally extinct, 64 as critically endangered, 75 as endangered, 74 as vulnerable, 58 as near threatened, 20 as least concern and 54 species as data deficient. Our results indicate that more than one-fourth of the epiphytic lichens of Italy are likely to be threatened, so that further research and effort are needed to include lichens in the main national conservation plans. Our results also highlight the lack of information that still hampers the rigorous evaluation of Italian lichens against IUCN criteria.     

The importance of host tree age, size and growth rate as determinants of epiphytic lichen diversity in boreal spruce forests

The amount of large and old trees has decreased in the boreal forests during the last centuries of forestry. Such trees are important habitats for epiphytic lichens and there is a growing concern for lichen species that are associated with large and old trees. However, only little is known about the relative importance of tree size versus age as determinants of lichen diversity. Here we have determined the size, age and growth rate of 157 Norway spruce trees and recorded the occurrence of epiphytic lichen species on their branches and lower stems. The study includes crustose lichens and was done in two old-growth forests in SE Norway. Tree age and tree size were the parameters that explained the largest part of epiphytic lichen diversity. Only the growth rate of the most recent time period, i.e. 1984–2004, showed a statistically significant relationship to diversity. There was no indication of a stabilising species number with increasing tree age. Slow-growing and old trees were, however, mainly of importance to the lichen species growing on stems, and this set of species were in general adversely affected by a large amount of branches. The opposite was the case for the species that were confined to branches as their diversity increased when the amount of branches increased. Our study adds empirical data to support the importance of large and old trees as bearers of biodiversity in boreal forests. Site preservation and patch retention of groups of old and large trees is recommended as measures to maintain epiphytic lichen diversity.     

The importance of host plant-habitat substrate in the maintenance of a unique isolate of the Sandhill Rustic: disturbance, shingle matrix and bare ground indicators

The Sandhill Rustic moth Luperina nickerlii leechi is an isolate restricted to the beach of Loe Bar in Cornwall UK; it is a UK Priority taxon because of its unique status and small, declining population. The larval foodplant is Sand Couch-grass Elytrigia juncea; the larvae feed at first inside the stems and then on the rhizomes underground. The distribution of the moth and E. juncea were investigated in this study in relation to substrate conditions and other plants. E. juncea has an above-ground clumped distribution; near the sea the plants are linked by rhizomes, but away from the sea the apparent clumping is a probable historic record of previous connectivity where the rhizomes have disappeared. The adult moths were found to be associated with more vigorous E. juncea plants growing in sparsely vegetated, more disturbed ground near the sea, especially those plants with large rhizome systems along which later instar larvae can travel between plants. Emerging moths were associated with areas of extensive E. juncea surrounded by bare ground, where there was a substantial variation of shingle particles between 125?μm and 8?mm. The absence of vegetation and associated roots apart from E. juncea, and a coarse particle mix, may allow larvae to move through the shingle and the moths to push their way upwards from their subterranean pupae. We conclude that management should aim to create areas of bare ground with extensive patches of E. juncea growing in coarser shingle, with extensive underground connectivity and few other plants.     

A quantitative study of the epiphytic vegetation on pollarded trunks of Fraxinus excelsior at Havrå, Osterøy,western Norway

The epiphytic vegetation on 19 pollarded trees of Fraxinus excelsior at the farm Havrå, Osterøy, western Norway was investigated. Each trunk was divided into a basal zone, a middle zone and a top zone. In each zone the four different aspects were analysed by squares (12 sampling units from each trunk). Within a total of 225 sampling units, 173 taxa were recorded (84 lichens, 72 bryophytes, 17 vascular plants). The epiphytic vegetation was classified into seven TWINSPAN groups, and it is shown by detrended correspondence analysis (DCA) that these groups are mainly separated by the first two DCA axes. In an attempt to explain the floristic composition, several environmental variables were measured, and the floristic and environmental data were analysed by canonical correspondence analysis (CCA). A pollarded tree, depending on its age, represents a continuum of perhaps several hundred years. Some of the recorded epiphytic lichens are very rare in Norway, and the pollarded trees thus contribute greatly to the biodiversity of the old cultural landscape. Several epiphytic species take advantage of favourable light conditions on trunks in the open fields. At Havrå, woodland has developed by tree colonization of old meadows and open fields during the last 40 years after the cessation of earlier managements. Some floristic differences between the epiphytic vegetation on trunks in the open fields and in the woodland are found. This suggests a change in the epiphytic vegetation because of the creation of a more shady habitat in parts of the area during a few decades.     

Gastropod grazing of epiphytic lichen-dominated communities depends on tree species

Tree species differ in longevity, canopy structure, and bark texture, chemistry and water storage. Tree species-specific traits play a role in shaping epiphytic vegetation and likely influence the community assembly of organisms feeding on epiphytes. Lichenivorous gastropods, species with calcium-rich shells in particular, need calcium and likely occur more abundantly in and around tree species with high available calcium. We quantified gastropod grazing on the epiphytic lichens Lobaria pulmonaria and Lobaria scrobiculata transplanted to blocks of adjacent trunks of Acer platanoides, Quercus robur and Tilia cordata. We tested the hypothesis that tree species known to have more available Ca, exhibit more grazing damage on transplanted lichens than trees with lower Ca-availability. The grazing pressure was 1.6–1.8 times higher for lichen transplants on Acer and Tilia known to produce litter with easily soluble Ca than on Quercus, which binds Ca as oxalate. Trees with a high grazing pressure on transplants had greater natural abundance of Lobaria virens than of L. pulmonaria. Gastropods preferred L. scrobiculata to L. pulmonaria, evidenced by more observed grazing marks and greater measured biomass loss. We attribute this difference to the lower concentration of carbon-based secondary compounds in L. scrobiculata. However, the strength of the preference varied between the three tree species receiving lichen transplants and was strongest on A. platanoides, while gastropods on T. cordata grazed equal amounts of each transplanted lichen. In conclusion, tree species influenced grazing patterns of gastropods on epiphytic lichens. In addition to bark pH and other factors, we have shown that tree species-specific differences in grazing pressure play a role in shaping the epiphytic macrolichen community.     

A survey method for assessing the richness of epiphytic lichens using growth forms

The species richness of epiphytic lichens is continuously decreasing by degradation and loss of habitat. Considering that taxonomic identification of all species is time and resource consuming, rapid assessment methods to extrapolate the total number of species are needed for practical conservation. This paper describes an alternative method using the correlation between lichens growth forms and species richness. The study was conducted in 406 forest stands located in Central Spain, covering a wide range of mediterranean-climate ecosystem regions, management intensity levels, canopy cover conditions, and tree sizes. The presence/absence of epiphytic lichens was determined in 6090 trees, which were dominated by oak species (Quercus ilex, Q. faginea, and Q. pyrenaica). In all type of forests, the diversity of growth forms was positively correlated with the total epiphytic lichen richness. In all cases, species richness increased in non-managed forest stands with dense canopies. Thus, we propose the use of lichen growth forms as a helpful surrogate of species richness to detect potentially conservation priority areas in the Mediterranean region.     

Epiphytic lichen is associated with species richness of gall-inducing aphids but not with niche differentiation among them

The presence of epiphytic foliose lichen amplifies the heterogeneity of habitat by creating shelters for insects living on tree bark. It thus should enhance species number and spatial niche segregation among these canopy insects. We studied this hypothesis in a field experiment using four aphid species that induce galls on Pistacia atlantica trees covered with Xanthoria parietina lichen. In autumn 2008, 3 months after aphid fundatrices were oviposited, we marked six branches on each of 29 trees. Two served as a control, whereas the other four were isolated with insect glue; two of them were scraped with sandpaper to remove epiphytic foliose lichens. We therefore obtained three treatments comprising control branches, isolated branches with lichen, and isolated branches without lichen. In summer 2009, we counted all the galls developing on five new annual shoots on each of 174 branches. We observed more cecidogenic aphid species on all the branches with lichens than without, but each species at different proportions. The different frequencies of utilization of the lichen did not lead to habitat partitioning between species. In conclusion, although habitat heterogeneity itself was associated with species richness and population abundance, it did not induce spatial niche segregation. Considering that many economically important insect species, pests and natural enemies, oviposit or spend some portion of their lives in bark cracks, it is possible that some can use lichens too for protection or/and oviposition sites. As a consequence, lichens may affect management of agrosystems and their impacts should be investigated more deeply in such contexts.     

The lichen flora of coastal saline lagoons in England

Abstract:The lichen flora associated with twenty saline lagoons in England is described. Though often scarce, lichens were present on shingle, miscellaneous stones, half-submerged concrete structures, retaining walls, salt marsh vegetation, wooden posts, and strand-line materials. Sites that had been modified by the activity of man often held richer assemblages than ones in a more natural condition. The lichen flora is a mixture of common-place species and maritime specialists. The large lagoon behind Chesil Beach, known as ‘The Fleet’, was the most important site surveyed. Many of the marine lichens present are typical of very sheltered coastlines. Caloplaca suaedae, found at two sites, is described as new to science.     

Analysis of the distribution of epiphytic lichens within homogeneousFagus sylvatica stands along an altitudinal gradient (Mount Olympos,Greece)

Epiphytic lichen vegetation onFagus sylvatica sas studied in 4 sites along an altitudinal gradient from 930 to 1500 m on SE facing slopes of Mount Olympos (Greece). The crucial factor determining the spatial heterogeneity of epiphytic lichens onF. sylvatica is the altitude and not the height on the trunk at which lichen community is established. 17 out of 26 taxa are confined to a particular elevation range, while another three are clearly ubiquitous in their distribution. The number of lichen species at breast height is higher than at the base of the trunks. The results were compared with those gathered earlier in an analogous study on the vertical distribution of epiphytic lichens onPinus nigra along an altitudinal gradient from 750 to 1510 m of the same mountain. Comparison suggests that spatial heterogeneity of epiphytic lichens onF. sylvatica is different from the one onP. nigra.